This invention relates to video processing.
For communication on a limited bandwidth digital channel, analog video is often encoded into a bitstream and the bitstream compressed. Decompression and conversion back to analog is done at the receiver end.
A compression technique that partially compensates for loss of quality involves separating the video data into two bodies of data prior to transmission: a “base” body of data and an “enhancement” body of data. The base data include a low-quality version of the video sequence, but can be transmitted using comparatively little bandwidth.
The enhancement data provide correction to the base data. Enhancement data may contain information to enhance the color of a region of a picture and to enhance the detail of the region of a picture. At the receiving end, the base data may be recombined with the enhancement data during the decoding process. Recombining the base data with all enhancement data will result in output video of quality very close to the original video. Because of communication channel bandwidth constraints, however, the full body of enhancement data often cannot be transmitted. Consequently enhancement data are divided into smaller subsets, each of which requires little bandwidth, and one or more subsets of enhancement data may be transmitted at the same time as the base data. Transmitting more enhancement data produces better output video, but requires more bandwidth.